On-car motor driving apparatus and self-diagnosing and selective driving mechanisms for the same

ABSTRACT

An on-car motor driving apparatus is equipped with a motor for moving a moving unit such as a window of a motor car, a motor driving controller which controls the revolution, stop, and rotational direction of the motor, and a current measuring and comparing device which measures the variation in current per unit time of the motor and compares the measured variation in current with a preset value. The on-car motor driving apparatus stops the revolution of the motor and/or reverses the rotational direction of the motor through the motor driving controller. The apparatus is further equipped with a voltage measuring device for measuring motor driving voltage and a voltage-based time setting device which changes the length of the unit time in accordance with the driving voltage value measured by the voltage measuring device. Line voltage is supplied to a differential amplifier only when the line voltage is supplied to the motor.

This application is a division of application Ser. No. 08/383,265, filedFeb. 3, 1995, now U.S. Pat. No. 5,578,912.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a motor driving apparatus for a powerwindow, power seat, etc. which are mounted on a passenger car or thelike and, more particularly, to an apparatus for detecting motorproblems such as lock-up, short circuit, and open circuit, and aselective driving mechanism for the motor.

2. Description of the Related Art

In recent years, more passenger cars and the like are equipped with apower window, which enables a passenger to open and close the window byoperating a switch, a power seat, which enables a passenger to adjustthe position of the seat or the angle of a seat back by operating aswitch, and other similar on-car apparatuses. Such a power window, powerseat, and other similar on-car apparatuses employ motors which use thevoltage from batteries mounted on passenger cars as their line voltage,the motors being driven to open and close the windows, move the seats,or operate other on-car apparatuses.

The on-car apparatuses stated above are provided with self-diagnosingdevices which detect motor failures such as lock-up, open circuit, andshort circuit and stop the motors so as to clear such failures.

FIG. 9 is a circuit diagram illustrative of an embodiment of such anon-car motor driving apparatus. The apparatus is equipped with a motor131, a selector switch 132 which has a moving contact terminal 132b, andfixed contact terminals 132a, 132c, a selector switch 133 which has amoving contact terminal 133b and fixed contact terminals 133a, 133c, acurrent value detecting resistor 136, a differential amplifier 137, anda microprocessor unit (MPU) 138 provided with an analog-to-digitalconverter (A/D converter).

The selector switches 132 and 133 are connected to the output side ofthe MPU 138 via a first inverter 134 and a second inverter 135,respectively; they are connected to the MPU 138 also via thedifferential amplifier 137 which detects the voltage across the twoterminals of the current value detecting resistor 136. An operatingswitch 139 is provided for controlling the direction in which movingunit moves and it is connected to the MPU 138. The current flowingthrough the motor 131 also flows through the current value detectingresistor 136 which is connected in series with the motor 131. Theselector switches 132 and 133 are energized by a driving output of theMPU 138 which is supplied via the first inverter 134 and the secondinverter 135, respectively. The terminal voltage of the current valuedetecting resistor 136 is detected by the differential amplifier 137 andthe detected terminal voltage is supplied to the MPU 138.

The following description gives an outline of the on-car motor drivingapparatus having the construction stated above.

In the drawing, if both selector switches 132 and 133 are set down inFIG. 9, i.e. if they are closed to make contact between 132b and 132cand between 133b and 133c, then the two terminals of the motor 131 areshort-circuited via the selector switches 132, 133, and no power issupplied to the motor 131 which, therefore, stays in a stationary state.Hence, a moving unit such as the window does not move at all.

If the moving contact of the selector switch 132 is moved up in FIG. 9to make contact between the moving contact terminal 132b and the fixedterminal 132a, with the selector switch 133 closed to make contactbetween terminals 133b and 133c, then a current path is formed from apower terminal 140, through the moving contact of the selector switch132, the motor 131, the moving contact of the selector switch 133, andthe current value detecting resistor 136 to ground. This lets currentflow into the motor 131, causing the motor to rotate in the forwarddirection. As a result, a moving unit such as the window is opened.

If the selector switch 133 is set up in the drawing to make contactbetween the moving contact terminal 133b and the fixed contact terminal133a, with the selector switch 132 kept in the down position in thedrawing, that is, with the moving contact terminal 132b and the fixedcontact terminal 132c kept in contact, then a current path is formedwhich leads to a from a power terminal 140, through the moving contactof the selector switch 133, the motor 131, the moving contact of theselector switch 132, and the current value detecting resistor 136 toground. This lets current, flowing in the opposite direction from thatin the preceding case, to pass through come into the motor 131, causingthe motor to rotate in the reverse direction. Thus, a moving unit suchas the window is closed. The selector switches 132 and 133 arecontrolled by the MPU 138 in accordance with the state of the switch 139which is controlled by a passenger.

Whether the motor runs in the forward or reverse direction, the motorcurrent flows through the current value detecting resistor 136,generating a voltage which corresponds to the motor current. Thegenerated voltage is amplified by the differential amplifier 137 whichis constituted by an operational amplifier. The output voltage of thedifferential amplifier 137 is sent to the MPU 138, then it is convertedto a digital value through the A/D converter. Based on the digitalvalue, the MPU 138 determines whether the motor 131 has incurred afailure or not. If the result of the determination indicates a problemwith the motor, the MPU 138 sets down the selector switches 132 and 133to stop the motor 131.

The on-car motor driving apparatus constructed as described above isdesigned so as to be able to detect an object that is caught at thewindow while the window is being closed.

More specifically, as illustrated in FIG. 10A illustrative of thechanges in motor current I, when the moment the motor 131 is started, aninrush current is produced, causing motor current I to rapidly rise andthen rapidly fall. When the motor 131 reaches a steady state and theinrush current ends, a low steady-state value is generated. When thewindow is completely closed and no longer makes any movement, motorcurrent I suddenly increases.

In the motor driving apparatus shown in FIG. 9, the MPU 138 sequentiallycaptures the digital value data which is obtained by subjecting theoutputs of the differential amplifier 137 to the A/D converter, then itdetermines the rate of change ΔI/Δt of the motor current from adifference ΔI between the digital values of two pieces of data whichhave been captured in succession. The MPU 138 then determines that themotor 131 has locked if the result of comparison of the rate of changewith a preset positive value K' is as shown below and it sets down theselector switches 132 and 133 to stop the motor:

    ΔI/Δt>K'

Thus, when the window is closed and the motor 131 is no longer allowedto rotate, motor current I suddenly increases as indicated by the solidline in FIG. 10A. This sudden rise can be detected and the motor 131 canbe stopped. The motor current suddenly increases as indicated by thesolid line shown in FIG. 10A also when the window locks in the middle ofclosing due to something caught at the window, preventing the motor 131from continuing its rotation. This, therefore, can also be detected andthe motor 131 can be stopped.

A motor employed for an on-car apparatus such as a power window andpower seat is equipped with two selector switches whereby switchingbetween the forward rotation and the reverse rotation can beaccomplished as described with reference to FIG. 9. FIG. 11 shows anexample of a motor selective driving mechanism employed when two motorsare involved. The motor selective driving mechanism is provided withmotors 101a and 101b and selector switches 102a, 102b, 103a, and 103b.

In the drawing, the same connection as that shown in FIG. 9 applies tothe connection between the selector switches 102a, 102b, 103a, and 103b,the power supply, and the grounding terminal, the self-diagnosing devicecomposed primarily of the resistor 136 shown in FIG. 9 being omitted inthis example. This construction allows the motor 101a to run in theforward or reverse direction or to be stopped by changing the setting ofthe selector switches 102a and 103a. In the same manner, the motor 101bcan be rotated in the forward or reverse direction or it can be stoppedby changing the setting of the selector switches.

FIG. 10 gives characteristic plots illustrative of the operatingcharacteristics of the known on-car motor driving apparatus. FIG. 10Ashows the changes in the current flowing through the motor 131; FIG. 10Bshows the changes in the lock current when the driving voltage of themotor 131 fluctuates. In FIGS. 10A and 10B, the axis of ordinateindicates the motor current; the axis of abscissa indicates time.

The current flowing through the motor 131 exhibits the changes as shownin FIG. 10A: the current value temporarily increases because of thelarge inrush current coming in during the period from time t0 to time t1which is the starting period of the movement of a moving unit such as awindow. After time t1, the revolution of the motor 131 reaches thestable state and a normal current of an approximately constant valueflows. When the revolution of the motor 131 is prevented because of anobject having been caught at a moving unit, e.g. a window, or because ofthe window having reached the moving end position in time t2, a lockcurrent, which increases within unit time Δt (t2˜t3) begins to flow.Reference character Vb denotes the voltage which is directly suppliedfrom a car battery; its voltage value may slightly change due to anexternal environmental factor or it may decrease as time elapses in thecourse of a prolonged use. In this case, as shown in FIG. 10B, the lockcurrent increases according to the driving voltage of the motor 131,i.e. voltage Vb supplied to the power terminal 140; the increasing curvegrows steeper as driving voltage Vb increases.

In the known on-car motor driving apparatus, as shown in FIG. 10B, unittime at for detecting current variation Δi is fixed; therefore, currentvariation Δi per unit time Δt significantly varies when driving voltageVb of the motor 131 fluctuates. Hence, current variation Δi per unittime Δt markedly varies with respect to any driving voltage Vb withinthe variation range. Accordingly, the known on-car motor drivingapparatus is designed to permit the detection of current variation Δiper unit time Δt on any driving voltage Vb in the variation range, andtherefore, a fixed value is provided as preset value Δis whichcorresponds to current variation Δimin per unit time Δt obtained fromminimum driving voltage Vbmin. With such preset value Δis selected,however, a large motor torque results if an object is caught in a movingunit when maximum driving voltage Vbmax or driving voltage Vb close tothe maximum driving voltage is being applied and the motor to beoverloaded. This calls for an emergency stop of the motor to prevent thecaught object from being damaged. For this reason, the circuit tends tobecome complicated.

Further, in the on-car motor driving apparatus illustrated in FIG. 9,whether the motor 131 is running or not, power is constantly suppliedfrom the battery to the power supply terminals of the operationalamplifier constituting the differential amplifier 137. Hence, theself-diagnosing device of the on-car motor driving apparatus constantlyconsumes power. The power window or power seat, however, is not usedvery often; therefore, the constant supply of power to theself-diagnosing device results in the wasteful consumption of a vastamount of power. This presents a serious problem especially when abattery provides the power source.

Furthermore, as shown in FIG. 10A, the on-car motor driving apparatusenables the detection of a failure in the middle of the operation of thepower window or power seat. If the apparatus were designed to determinethat a failure has occurred whenever the comparison result indicatesΔI/Δt>K' as described above, then the following problem would arise:motor current I at the time of start of the motor 131 rapidly increasesbecause it develops an inrush current as shown in FIG. 10A, and sincethe rate of variation ΔI/Δt of motor current I at that time wouldsatisfy the expression given above, the MPU would determine that afailure has occurred and consequently stop the motor 131. As a result,the opening or closing of the power window, for example, would beinterrupted.

To avoid the problem mentioned above, the known self-diagnosing deviceis designed not to detect a failure of the motor 131 during inrushcurrent generating period T (e.g. 100 msec) before motor current Ireaches the steady-state current since the start-up of the motor 131.This, however, gives rise to the following inconvenience: in the case ofa power window, for example, when the motor 131 is actuated to close thewindow, which has been closed halfway, with something stuck in thewindow, the motor 131 is allowed to run only for a short time periodbefore it is brought to a stop. Therefore, the rising motor current Idue to the failure overlaps the inrush current at the time of thestart-up, making it impossible detect the failure because it happensduring the period when the inrush current takes place.

Furthermore, in the selective driving mechanism of the on-car motordriving apparatus shown in FIG. 11, each motor requires two selectorswitches. Hence, as the number of motors increases, the required numberof selector switches increases accordingly. The selector switches arecostly relay switches which are controlled by a microprocessor unit. Anincrease in the number of required selector switches therefore addsgreatly to the price of the power window, power seat or othercar-mounted apparatus.

SUMMARY OF THE INVENTION

The first object of the present invention is to provide an on-car motordriving apparatus wherein the motor load is maintained at a constantlevel even when an object is stuck in a moving unit regardless of thefluctuation in the motor driving voltage.

The second object of the present invention is to provide aself-diagnosing device of a motor for an on-car apparatus, whichself-diagnosing device being capable of achieving dramatically reducedpower consumption by supplying power only when the motor is operated.

The third object of the present invention is to provide aself-diagnosing device for an on-car apparatus, which self-diagnosingdevice being capable of detecting a motor failure even at the time ofstart-up.

The fourth object of the present invention is to provide a motor drivingdevice for an on-car apparatus, which motor driving device enables areduced number of switching means and permits the selection between thereverse rotating direction and the forward rotating direction of aplurality of motors.

To these ends, according to the present invention, there is provided amotor driving apparatus which is provided with a motor for moving amoving unit, a motor driving controller for controlling starting,stopping, and rotational direction of the motor, and a current measuringand comparing device which measures the variation in current per unittime of the motor and compares the variation in current with a presetvalue; the motor driving apparatus being able to stop the revolution ofand/or reverse the rotational direction of the motor through the motordriving controller when a current variation exceeding the preset valueis detected through the current measuring and comparing device, andbeing further equipped with a voltage measuring device for measuring themotor driving voltage and a voltage-based time setting device forchanging the length of the aforesaid unit time in accordance with thedriving voltage value measured by the voltage measuring device.

Further, the motor driving apparatus according to the present inventiondetermines that the motor has incurred a failure if the rate ofvariation of the motor current ΔI/Δt with respect to value K, which is apreset sufficiently small positive value, is ΔI/Δt<-K.

The motor driving apparatus according to the present invention isfurther provided with a first switching means for selectively connectingthe terminals on one side of respective motors to either a battery orthe ground, a second switching means for selecting one of the terminalson the other side of the respective motors, and a third switching meansfor selectively connecting the second switching means to either thebattery or the ground.

The motor driving apparatus according to the present invention isprovided with a voltage measuring device for measuring the motor drivingvoltage and a voltage-based time setting device which detects thevariation in motor current from the driving voltage value measured bythe voltage measuring device and changes the length of the unit time inaccordance with the detected variation in current, so that, if thedriving voltage is lower than a normal voltage value, then the length ofthe unit time is increased according to the voltage value, or if thedriving voltage is higher than the normal voltage value, then the lengthof the unit time is decreased.

Thus, the length of the unit time is changed in accordance with themotor driving voltage; therefore, the variation per unit time in thecurrent flowing through the motor no longer depends on the drivingvoltage value, enabling a fixed amount of variation in current at alltimes. This makes it possible to maintain constant motor torque andmotor load when a stuck object is detected, regardless of thefluctuation in the driving voltage.

According to another example, power is supplied to the amplifier onlywhile the switch is ON and the motor is running, thereby preventing theamplifier from wastefully consuming power.

Furthermore, even if the motor incurs a failure due to something caughtin the window or the like at the start-up of a large motor and the motorcurrent develops on the start-up of the motor, disabling the motor fromrunning and maintaining the current value at the large inrush current,the value does not rapidly go down to the steady-state current valuewhich is a small value. Thus, it is determined that the motor is in anabnormal condition at the time of start-up if the motor current does notrapidly decrease from the inrush current to the steady-state current,and if rate of variation in motor/current, ΔI/Δt, is smaller than anegative value -K which is sufficiently small, then it means that themotor current did not rapidly fall from the inrush current to thesteady-state current, thus making it possible to determine that themotor has a problem at the time of start-up.

In addition, the first and third switching means function to selectwhether the motors should be connected to the battery or grounded inaccordance with the direction of the rotation of the motors. Hence, thenumber of the switching means does not increase even when the number ofthe motors increases; only the scale of the second switching means forselecting the motors increases, the scale being increased just inproportion to the number of the switching means. There will be lesschance, therefore, of an increase of the number of switching means thanin the known embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit block diagram illustrative of the construction of anembodiment of an on-car motor driving apparatus in accordance with thepresent invention;

FIG. 2A is a characteristic chart illustrative of the operatingcharacteristics of the on-car motor driving apparatus according to theembodiment shown in FIG. 1; it shows the changes in the lock currentflowing through the motor 1, the changes being caused by the fluctuationof line voltage (driving voltage) Vb;

FIG. 2B is a characteristic chart illustrative of the operatingcharacteristics of the on-car motor driving apparatus according to theembodiment shown in FIG. 1; it shows the changes in unit time Δt causedby the fluctuation of line voltage (driving voltage) Vb;

FIG. 3 is a flowchart showing the operation sequence of the on-car motordriving apparatus according to the embodiment shown in FIG. 1;

FIG. 4 is a circuit diagram illustrative of an embodiment of aself-diagnosing device of an on-car motor driving apparatus inaccordance with the present invention;

FIG. 5 is a circuit diagram illustrative of the construction of theembodiment shown in FIG. 4, two motors being included in theconstruction;

FIG. 6 shows the changes in the motor current shown in FIG. 4, thechanges being caused by a failure of the motor at the time of start-up;

FIG. 7 is a flowchart showing a series of operations performed inrelation to the motor current shown in FIG. 6 for detecting a motorfailure which takes place when the motor is started;

FIG. 8 is a circuit diagram illustrative of an embodiment of a selectivedriving mechanism of the motor for an on-car apparatus in accordancewith the present invention;

FIG. 9 is circuit block diagram illustrative of the schematicconstruction of an example of a known on-car motor driving apparatus;

FIG. 10A is a characteristic chart illustrative of the operatingcharacteristics of the known on-car motor driving apparatus; it showsthe changes in the lock current flowing through the motor 131, thechanges taking place when line voltage (driving voltage) Vb fluctuates;

FIG. 10B is a characteristic chart illustrative of the operatingcharacteristics of the known on-car motor driving apparatus; it showsthe changes in unit time Δt which takes place when line voltage (drivingvoltage) Vb fluctuates; and

FIG. 11 is a circuit diagram illustrative of an example of a selectivedriving mechanism of the known on-car motor driving apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention will be described in detailwith reference to the accompanying drawings.

FIG. 1 is the circuit block diagram illustrative of the construction ofthe embodiment of the on-car motor driving apparatus in accordance withthe present invention.

In FIG. 1, the motor 1 is a DC motor with one end thereof connected tothe moving contact of a first relay 2 and the other end thereofconnected to the moving contact of a second relay 3, so that current islet flow into the motor 1 in one direction or in the opposite directionfrom that, or the supply of current to the motor 1 is stopped bychanging the connection of the moving contacts of the first relay 2 andsecond relay 3. The current of the motor 1 flows to a grounding pointthrough a current value detecting resistor 6 which is connected inseries with the motor 1. The first relay 2 and the second relay 3 areenergized or de-energized in accordance with a driving output suppliedfrom a microprocessor unit (MPU) 8, i.e. the output levels of the OPENand CLOSE terminals of the MPU 8, via a first inverter 4 and a secondinverter 5, respectively. The current value detecting resistor 6 has itsboth ends connected to the two input terminals of a differentialamplifier 7; the terminal voltage thereof is detected by thedifferential amplifier 7 and supplied to the MPU 8. A first potentialdividing resistor 11 and a second potential dividing resistor 12 areconnected between a power terminal 10 and a grounding point. A potentialdividing output of the line voltage (driving voltage) Vb which isobtained at the grounding point of the first potential dividing resistor11 and the second potential dividing resistor 12 is supplied to the MPU8. A switch 9 is used to move a moving unit (actuator); it is providedfor each moving direction of the moving unit and connected to the MPU 8.

The MPU 8 incorporates a motor driving controller which controls therevolution and stop of the motor 1 and also the direction of rotation ofthe motor 1; a current measuring and comparing device which measures thevariation in current per unit time during which the driving currentflows through the motor 1, compares the measured variation in currentwith a preset value, and supplies, when the variation in current exceedsthe preset value, the detected output to the motor driving apparatus; avoltage measuring device which measures driving voltage Vb of the motor1; and a voltage-based time setting device which changes the length ofthe unit time in accordance with the magnitude of driving voltage Vbmeasured by the voltage measuring device. In this case, the MPU 8carries out the internal data processing digitally and the enteredanalog data such as voltage is converted to digital data before it issubjected to required processing. The motor 1 is designed to actuate amoving unit such as a window, sunroof, and seat of a car when it isdriven.

The on-car motor driving apparatus which is configured as describedabove performs the following operations. In this embodiment, it isassumed that the moving unit, which is moved when the motor 1 is driven,is a window.

The on-car motor driving apparatus according to this embodiment operatesin the same manner as the known on-car motor driving apparatus alreadydiscussed; it sets the outputs of the OPEN and CLOSE terminals of theMPU 8 at low-level voltage (L). The low-level voltage (L) is changed tohigh-level voltage (H) by the first inverter 4 and the second inverter 5and the high-level voltage (H) is applied to the ends on one side of thefirst relay 2 and the second relay 3. In this case, the high-levelvoltage (H) is applied to the ends on the other side of the first relay2 and the second relay 3 at all times; therefore, the first relay 2 andthe second relay 3 are not energized, the moving contacts thereof beingset to the fixed contact side (set down in FIG. 1). Thus, no current issupplied to the motor 1 and the window does not move at all.

The on-car motor driving apparatus according to this embodiment alsoperforms the same operation as the known on-car motor driving apparatuswhen opening the window; it switches the output of only the OPENterminal of the MPU 8 from the low-level voltage (L) to the high-levelvoltage (H). The high-level voltage (H) is switched-to the low-levelvoltage (L) by the first inverter 4 before it is supplied to one end ofthe first/relay 2. This energizes the first relay 2 and the movingcontact of the first relay 2 is switched from one fixed contact (thedown position in FIG. 1) to the other fixed contact (the up position inFIG. 1). At this time, the moving contact of the second relay 3 is stillin the original set position; therefore, a current path is formed whichleads to the grounding point-via the power terminal 10, the movingcontact of the first relay 2, the motor 1, the moving contact of thesecond relay 3, and the current value detecting resistor 6. The formedcurrent path lets current flow through the motor 1 to open the window,the current flowing from the bottom toward the top in FIG. 1.

The on-car motor driving apparatus according to this embodiment alsoperforms the same operation as the known on-car motor driving apparatuswhen closing the window which is stationary; it switches the output ofonly the CLOSE terminal of the MPU 8 from the low-level voltage (L) tothe high-level voltage (H). The high-level voltage (H) is switched tothe low-level voltage (L) by the second inverter 5 before it is suppliedto one end of the second relay 3. This energizes the second relay 3.Since the moving contact of the second relay 3 is still in contact withone fixed contact (the down position in FIG. 1), a current path isformed which leads to the grounding point via the power terminal 10, themoving contact of the second relay 3, the motor 1, the moving contact ofthe first relay 2, and the current value detecting resistor 6. Theformed current path lets current to flow through the motor 1 to close amoving unit, e.g. a window, the current flowing in the oppositedirection from that in the preceding case.

The following will describe how the motor driving apparatus behaves ifsome object is caught in a window which is moving in a certain directionwhile the motor 1 is being driven or the window reaches a moving limitpoint, causing the lock current to flow through the motor 1.

In this embodiment, when the motor 1 is driven, the current flowingthrough the motor 1 also flows through the current value detectingresistor 6. Therefore, the value of the current flowing through themotor 1 can be determined from the output voltage of the differentialamplifier 7 by detecting the terminal voltage of the current valuedetecting resistor 6 through the differential amplifier 7. The outputvoltage is supplied to the current measuring and comparing device in theMPU 8 and the output voltage is converted to a digital output. Thecurrent measuring and comparing device is equipped with a built-in timercircuit for marking unit time Δt; it measures the difference between thedigital output voltage at the moment the timer circuit is actuated andthat at the moment the timer circuit marks the set time, that is, itmeasures current variation Δi per unit time Δt of the motor 1, and itcompares the measured current variation Δi with a preset value stored inthe current measuring and comparing device.

If the lock current starts to flow through the motor 1 because somethinghas stuck in the window or the window has reached its moving limitpoint, resulting in a sudden rise in the current value, then the currentmeasuring and comparing device detects that the variation in current hasexceeded the preset value and issues a detection output which issupplied to the motor driving controller also included in the MPU 8. Inresponse to the detection output, the motor driving controller switchesthe output of the OPEN terminal or CLOSE terminal of the MPU 8 from thehigh level (H) to the low level (L) to stop the revolution of the motor1, thereby stopping the movement of the window. If necessary, the motordriving controller reverses the revolution of the motor 1 by invertingthe output voltage levels of the OPEN terminal and CLOSE terminal,thereby moving the window in the reverse direction.

In the embodiment, line voltage Vb (the driving voltage of the motor 1)supplied to the motor 1 is supplied to the first potential dividingresistor 11 and the second potential dividing resistor 12, the voltageat the connection point of the first and second potential dividingresistors 11, 12 being supplied to the voltage measuring device in theMPU 8 as a power-dependent voltage which represents the fluctuation inthe line voltage (driving voltage) Vb. The voltage measuring deviceconverts the power-dependent voltage into digital data and supplies itto the voltage-based time setting device in the MPU 8. The voltage-basedtime setting device changes the length of unit time Δt of the currentmeasuring and comparing device in accordance with the receivedpower-dependent voltage which has been converted to digital data. If thenormal value of line voltage (driving voltage) Vb is set to 12 V, forexample, the value applied when line voltage (driving voltage) Vbfluctuates over 12 V is set to 16 V, for example, and the value appliedwhen line voltage (driving voltage) Vb fluctuates below 12 V is set to 9V, for example, then the voltage-based time setting device sets thelength of unit time Δt to the normal length Δt1 when line voltage(driving voltage) Vb is 12 V, or sets the length of unit time Δt to Δt0,which is shorter than Δt1, when line voltage (driving voltage) Vb is16V, or it sets the length of unit time Δt to Δt2, which is longer thanΔt1, when line voltage (driving voltage) Vb is 9 V. Further, thevoltage-based time setting device changes the length of unit time Δt inaccordance with the voltage value when the line voltage (drivingvoltage) Vb lies between 16 V and 12 V or between 12 V and 9 V.

FIG. 2 are the characteristic charts showing the operatingcharacteristics of the on-car motor driving apparatus according to theembodiment. FIG. 2A shows the changes in the lock current flowingthrough the motor 1, the changes being caused by the fluctuation of linevoltage (driving voltage) Vb; FIG. 2B shows the changes in unit time atcaused by the fluctuation of line voltage (driving voltage) Vb.

In FIG. 2A, the axis of ordinate indicates the motor current and theaxis of abscissa indicates time. In FIG. 2B, the axis of ordinateindicates unit time Δt and the axis of abscissa indicates line voltage(driving voltage) Vb.

As illustrated in FIG. 2B, with the length of unit time Δt set as thenormal length Δt1 when line voltage (driving voltage) Vb is thesteady-state value of 12 V, if line voltage (driving voltage) Vbfluctuates over the steady-state value 12 V, then the length of unittime Δt is made shorter than the aforesaid Δt1 according to thefluctuation, or if line voltage (driving voltage) Vb fluctuates belowthe steady-state value of 12 V, then the length of unit time at is madelonger than the aforesaid Δt1 according to the fluctuation.

Further, as shown in FIG. 2B, the curve of the lock current flowing intothe motor 1 indicates a steeper increase when line voltage (drivingvoltage) Vb is 16 V, which is larger than the steady-state value, 12 V,than the increase observed when line voltage (driving voltage) Vb is thesteady-state value, 12 V; conversely, the increase curve is gentler whenline voltage (driving voltage) Vb is 9 V which is smaller than thesteady value, 12 V. A constant detection level of current variationvalue Δi of the motor 1, i.e. a constant level of current variationvalue Δi based on which an output of the comparison between currentvariation value Δi and the preset value is obtained, can be maintainedregardless of the fluctuation of line voltage (driving voltage) Vb bychanging the length of unit time Δt in accordance with the steepness ofthe increase curve of the lock current as follows: the length of unittime Δt for line voltage (driving voltage) Vb of 16 V, for example, ischanged to Δt0, which is shorter, when the lock current increase issteep; if the lock current increase is steep with respect to Δt1 of unittime at for line voltage (driving voltage) Vb of the steady-state value,12 V, then the length of unit time Δt for line voltage (driving voltage)Vb of 16 V, for example, is changed to Δt0 which is shorter than theaforesaid Δt1; if the lock current increase is gentle, then the lengthof unit time Δt for line voltage (driving voltage) Vb of 9 V, forexample, is changed to Δt2 which is longer than the aforesaid Δt1.

Thus, according to the embodiment, unit time Δt is changed in accordancewith the fluctuation of line voltage (driving voltage) Vb of the motor 1and therefore current variation Δi per unit time at no longer depends online voltage (driving voltage) Vb. This makes it possible to detect afixed amount of current variation in the motor 1 at all times;therefore, both the motor torque and motor load at the time when a stuckobject is detected can be maintained at a fixed level, ensuring stableoperation.

FIG. 3 is the flowchart showing the operation sequence of the on-carmotor driving apparatus according to the embodiment; it summarizes theoperation of the motor driving apparatus according to the embodimentdiscussed above.

Referring to FIG. 3, the operation of the motor driving apparatusaccording to the embodiment will be explained again. In this flowchartalso, the moving unit is assumed to be a window, and the example refersto the operation for opening the window.

To begin with, the opening switch 9 is pressed in step S1 and the MPU 8sends output voltage of high level (H) to the OPEN terminal. In thesubsequent step S2, the output voltage of high level (H) applied by theMPU 8 energizes the first relay 2, causing current to flow through themotor 1. At this time, the window begins to move in the openingdirection. In step S3, the current measuring and comparing device in theMPU 8 measures the terminal voltage of the current value detectingresistor 6 which has been detected through the differential amplifier 7and reads the current i0 flowing through the motor 1. Then, in step S4,the voltage measuring device of the MPU 8 reads the voltage at theconnection point of the first and second potential dividing resistors 11and 12, i.e. the power-dependent voltage which represents line voltage(driving voltage) Vb. In step S5, the voltage-based time setting deviceof the MPU 8 calculates and sets unit time Δt in the current measuringand comparing device in accordance with the power-dependent voltagewhich has been read through the voltage measuring device. Then, in stepS6, the current measuring and comparing device starts the built-in timercircuit. In step S7, the MPU 8 determines whether the set unit time Δtmentioned above has elapsed since the timer circuit was started. If unittime Δt has elapsed, then the program proceeds to the next step S8; ifunit time Δt has not yet elapsed, then the same step S7 is repeated.

Next, in step S8, the current measuring and comparing device measuresagain the terminal voltage of the current value detecting resistor 6which has been detected by the differential amplifier 7 and readscurrent i1 flowing through the motor 1. In step S9, the currentmeasuring and comparing device determines the difference between the tworead currents i0 and i1, i.e. current variation Δi (i1-i0) per unit timeΔt. In step S10, the current measuring and comparing device comparescurrent variation Δi with preset value Δis. If the comparison resultindicates Δis>Δi, then the program goes back to step S3 to repeat thesteps from S3 and after; if the comparison result indicates Δis≧Δi, thenthe program proceeds to the next step S11. Lastly, in step S11, theoutput voltage of high level (H) of the OPEN terminal or CLOSE terminalreceived from an MPU 8 is switched to the low level (L) output voltageso as to stop energizing the first relay 2 or the second relay 3,thereby cutting off the current supplied to the motor 1. This causes thewindow to stop moving in the opening direction. Further, in step S11, asnecessary, the levels of the output voltage of the OPEN terminal and theCLOSE terminal sent from the MPU 8 are inverted to reverse the energizedand unenergized states of the first relay 2 and the second relay 3 inorder to switch the direction of the window moving in the flowingdirection of current for driving the motor 1 to the closing direction.

In the embomiment described above, a single microprocessor 8incorporates the motor driving controller, the current measuring andcomparing device, the voltage measuring device, and the voltage-basedtime setting device. The present invention, however, is not limited tosuch embodiment; the respective devices mentioned above may beconfigured discretely or may be incorporated in two or moremicroprocessors.

Further, in the example described above, the steady-state value of linevoltage (driving voltage) Vb is 12 V and the fluctuation of line voltage(driving voltage) ranges from 9 V to 16 V. The steady-state value andfluctuation range of line voltage (driving voltage) Vb in the presentinvention, however, are not limited to them; they may be changedaccording to individual cases.

Furthermore, in the embodiment given above, the current value detectingresistor 6 and the differential amplifier 7 are used as the currentdetecting means for detecting current i0 and i1 flowing through themotor 1; and the first and second potential dividing resistors 11 and 12are used as the voltage detecting means for detecting line voltage(driving voltage) Vb; the current detecting means and the voltagedetecting means in the present invention, however, are not limited tothe constructions mentioned above; it is apparent that other means maybe employed.

Another embodiment of the present invention will now be described inconjunction with the accompanying drawings.

FIG. 4 is the circuit diagram illustrative of an embodiment of aself-diagnosing device of an on-car motor driving apparatus inaccordance with the present invention. In the drawing, the anode of adiode 56 is connected between the moving contact of a selector switch 52and one terminal of a motor 51; the anode of a diode 57 is connectedbetween the moving contact of a selector switch 53 and the otherterminal of the motor 51. The cathodes of both diodes 56 and 57 areconnected to the power terminal of an operational amplifier constitutinga differential amplifier 55. These selector switches 52 and 53 are relayswitches, for example, and they are controlled by the MPU in response tooperational action taken by a passenger.

In such a construction, if the selector switches 52 and 53 are set tomake contact with B side, so that battery voltage +B is not applied tothe motor 51, keeping the motor at rest, then no positive batteryvoltage is applied to the anodes of the diodes 56 and 57; therefore, noline voltage is applied to the operational amplifier. This means that nopower is consumed by the differential amplifier while the motor 51 is atrest.

If the selector switch 52 is set to the A side and the switch 53 to theB side to cause the motor 51 to rotate in the forward direction, thenthe battery voltage +B is supplied as the line voltage to theoperational amplifier via the selector switch 52 and the diode 56. Thisactuates the differential amplifier 55 and the self-diagnosis of themotor 51 is carried out. Further, if the selector switch 52 is set tothe B side and the switch 53 to the A side to cause the motor 51 torotate in the reverse direction, then the battery voltage +B is suppliedas the line voltage to the operational amplifier via the selector switch53 and the diode 57. This actuates the differential amplifier 55 and theself-diagnosis of the motor 51 is carried out.

Thus, according to this embodiment, only when the battery voltage +B isapplied and the motor 51 requires self-diagnosis, the line voltage issupplied to the amplifier 55 to perform the self-diagnosis. Thisprevents the self-diagnosing device from wastefully consuming powerwhile no battery voltage +B is being applied to the motor 51, therebydramatically reducing the power consumed by the self-diagnosing device.

FIG. 5 shows a case wherein two motors are employed in the embodimentshown in FIG. 4. The apparatus in FIG. 5 is provided with a motor 51',selector switches 52', 53', a current value detecting resistor 54', adifferential amplifier 55', and diodes 56', 57'; the components whichcorrespond to those shown in FIG. 4 will be assigned the same referencenumerals, overlapping explanation being omitted.

The example shown in the drawing has the motor 51' which has been addedto the motor 51 equipped with the self-diagnosing device which isconstituted by the resistor 54, the differential amplifier 55, etc. asin the case of the embodiment shown in FIG. 4. The motor 51' is alsoequipped with a self-diagnosing device constituted by the resistor 54',the differential amplifier 55', etc.

As in the case of the motor 51, the anode of the diode 56' is connectedbetween the moving contact of the selector switch 52' and one terminalof the motor 51', and the anode of the diode 57' is connected betweenthe moving contact of the selector switch 53' and the other terminal ofthe motor 51' The cathodes of both diodes 56' and 57' are connected tothe power terminal of the operational amplifier constituting thedifferential amplifier 55'.

If it is assumed that the MPU controls either the selector switches 52,53 or the selector switches 52', 53' and one or both of the motors 51and 51' rotate, then the battery voltage +B is applied as the linevoltage to the differential amplifiers 55, 55', causing bothself-diagnosing devices 55, 55' to operate. In this case, if only onemotor, the motor 51, for example, is rotated, the MPU senses it andtherefore does not capture the output of the dormant differentialamplifier, i.e. the operational amplifier 55' in this case.

In this way, the same operation is carried out even/when three or moremotors are employed. It is possible to apply the line voltage to theself-diagnosing device only when the line voltage is applied to themotor even when a plurality of motors are used.

Alternatively, the line voltage may be applied only to the differentialamplifier of the self-diagnosing device of the motor to which thebattery voltage +B is applied.

FIG. 6 shows the changes in the motor current caused by a failure of themotor at the time of start-up.

As explained with reference to FIG. 9, the known on-car motor drivingapparatus is designed to be actuated after the inrush current period ofthe motor current is over. This embodiment is designed to be actuatedupon the start-up of the motor.

In FIG. 4, taking a power window as an example, if something is stuck inthe window while the motor 51 is at rest and if the motor 51 is startedwith the stuck object stuck in the window, then the motor currentchanges as illustrated in FIG. 6. More specifically, the moment themotor 51 is started, motor current I suddenly rises and develops theinrush current. Although the motor 51 attempts to run, it is allowed torotate only slightly before it is halted. Motor current I passes thepeak of the inrush current and slightly goes down but it maintains thelarge current value

The MPU continues to capture the data which is obtained by subjectingthe outputs of the differential amplifier 55 to the A/D conversion sincethe motor 51 was started, determines difference ΔI between the digitalvalues of two pieces of data captured in succession, and furtherdetermines rate of variation ΔI/tΔof the motor current, which rate isobtained by dividing difference ΔI by period at of the sampling pulse ofthe A/D converter. The MPU then compares the determined rate ofvariation ΔI/Δt with a preset sufficiently small negative value -K inorder to decide whether the motor 51 has a failure or not.

If the motor 51 has a failure from the start-up thereof as stated above,rate of variation becomes ΔI/Δt<-K as soon as the peak of the inrushcurrent of the motor current is over, thus enabling the MPU to detectthe failure of the motor. The MPU, upon the detection of the failure,switches the connection of the selector switches 52, 53 to the B side tostop the motor 51 or changes the contact of the selector switches 52, 53to rotate the motor 51 in the reverse direction to open the window asshown in FIG. 4.

Thus, if, for example, a part of passenger's body should be caught inthe window as soon as the motor 51 is actuated, the window can beimmediately stopped or opened.

If an object is stuck in the window, preventing the motor 51 fromcontinuing its revolution after the inrush current phase of motorcurrent I is over, then the MPU behaves in the same manner as the knownself-diagnosing device explained with conjunction with FIG. 9.Specifically, the MPU detects the relationship between variation rate ofthe detected motor current ΔI/Δt and a preset large positive value K',that is, ΔI/Δt>K', and it determines that the motor 51 has incurred afailure, then it either stops the motor 51 or inverts the revolution ofthe motor 51 as described above.

FIG. 7 is the flowchart showing the operations described above.

In the flowchart, a series of operations in steps 42, 43, and 44 isrepeated during the inrush current period of the motor current (theperiod is set to 100 msec in this example). If no failure with the motor51 is detected during the period, then the series of operations in thesteps 45, 46, and 47 is repeated until the opening or closing of thewindow is completed or until the motor 51 can no longer rotate becauseof an object stuck in the window. If the window is closed or somethingis caught in the window in the middle of closing, then it is detected inthe step 47 and the safety operation stated above is carried out to stopthe motor 51 (step 49). The operations discussed above are the same asthose explained in conjunction with FIG. 9.

If the motor 51 incurs a failure as stated above during the inrushcurrent period, then the failure is detected in the step 43 and thesafety operation is carried out (step 48) to stop the motor 51.

If the operation for stopping the motor 51 is performed in the middle ofthe opening or closing of the window, then the microprocessor detects it(step 45) and stops the motor 51 (step 49).

Although the power window is taken as an example to describe theinvention in the description given above, other on-car apparatusesincluding a power seat can be taken as examples in the same manner forthe purpose of describing the invention.

FIG. 8 is the circuit diagram illustrative of the embodiment of aselective driving mechanism of the motor for an on-car apparatus inaccordance with the present invention. Reference numerals 51a and 51bdenote motors and 58 to 60 denote selector switches.

In the drawing, the terminals on one side of the two motors 51a and 51bare connected to moving contact C of the selector switch 58, fixedcontact A of the selector switch 58 is connected to the battery, andfixed contact B is connected to the grounding terminal. The terminals onthe other side of the motors 51a and 51b are connected to fixed terminalD and fixed terminal E, respectively, of the selector switch 59, themoving contact of the selector switch being connected to the movingcontact of the selector switch 60. Fixed contact A of the selectorswitch 60 is connected to the battery and fixed contact B to thegrounding terminal.

The selector switch 59 is used to select either 51a or 51b to be driven.The selector switches 58 and 60 are used to decide the rotationaldirection of the selector motor. The selector switches 58, 59, and 60are controlled by the MPU in response to operational action taken by apassenger.

When it is assumed that the selector switches 58 and 60 are both incontact with fixed contacts B, even if a motor has been selected throughthe selector switch 59, the motor does not run because both terminals ofthe motor are grounded.

If the selector switch 58 is brought in contact with contacts A and theselector switch 60 is brought in contact with contacts B, with theselector switch 59 set to select the motor 51a, then the motor currentflows from the battery of +B voltage to the grounding terminal via theselector switch 58, the motor 51a, and the selector switches 59 and 60,causing the motor 51a to run. When it is assumed that the motor 51a isrunning in the forward direction at this time, if the selector switch 58is brought in contact with fixed contact B and the selector switch 60 incontact with fixed contact A, then the motor current flows from thebattery of +B voltage to the grounding terminal via the selectorswitches 60 and 59, the motor 51a, and the selector switch 58, causingthe motor 51a to run in the reverse direction. The same operationapplies when the motor 51b is selected by the selector switch 59.

Thus, a desired motor can be selected and controlled to stop or reversethe rotation.

The embodiment will now be compared with the known mechanism shown inFIG. 11 wherein two motors are employed. In comparison with the knownmechanism which requires four selector switches 102a, 102b, 103a, and103b, the embodiment requires only three selectors switches, reducingthe required number of switches by one. In general, when n (provided "n"is an integer of 2 or greater) motors are used, 2n selector switches arerequired to drive the motors as shown in FIG. 11. In the case of theembodiment, only one each of the selector switch 58 and the selectorswitch 60 is required regardless of the number of motors involved, onlythe selector switch 59 being a complicated switch which has n movingcontacts. As the selector switch 59, a relay switch which opens andcloses can be used. When such relay switches are used for n motors, nrelay switches are required. In this case, while the total number ofnecessary switches will be 2n when the motors are connected asillustrated in FIG. 11, the total number will be (n+1) in theembodiment, obviously indicating a reduced number of required switches.

In this embodiment also, each motor can be provided with theself-diagnosing device as shown in FIG. 5.

Thus, according to the present invention, the on-car motor drivingapparatus is provided with a voltage measuring device which measuresmotor driving voltage Vb and a voltage-based time setting device whichdetects motor current variation Δi from the driving voltage valuemeasured by the voltage measuring device and changes the length of unittime Δt according to current variation Δi; therefore, if driving voltageVb is lower than the normal voltage value, then the length of unit timeΔt is increased according to the voltage value, or if driving voltage Vbis higher than the normal voltage value, then unit time Δt is decreasedaccording to the voltage value.

Since the length of unit time Δt is changed in accordance with the motordriving voltage value, variation Δi per unit time Δt of the currentflowing through the motor 1 no longer depends on the driving voltagevalue. This makes it possible to detect a fixed amount of currentvariation in the motor 1 at all times, providing an advantage in thatboth motor torque and motor load at the time when a stuck object isdetected can be maintained at a constant level regardless of thefluctuation in the driving voltage.

Further, according to the present invention, since line voltage issupplied to the amplifier of the self-diagnosing device only when thebattery voltage is applied to a motor, wasteful power consumption by theamplifier can be eliminated, leading to a significant reduction in powerconsumed by the self-diagnosing device.

Furthermore, according to the present invention, a motor failure can bedetected from the moment the motor is started, making it possible toprevent an object from being caught in a window.

In addition, according to the present invention, the number of switchingmeans used for a plurality of motors can be reduced, contributing to theachievement of a simpler structure and lower price of the mechanism.

What is claimed is:
 1. A motor driving apparatus for applying a motordriving voltage to a motor, the motor being connected to a moving unitmounted on a vehicle, the moving unit being movable in a forward orreverse direction by the motor in response to a command signal enteredby a passenger, the apparatus comprising:a switching circuit forconnecting the motor driving voltage to the motor such that a motordrive current passes through the motor in one of a forward and a reversedirection in response to a switching signal; means for measuring themotor drive current; and a controller for transmitting the switchingsignal in response to the command signal, the controller including meansfor measuring a variation in the motor drive current and for comparingthe motor drive current variation with a preset value; wherein saidmeans for measuring the motor drive current comprises a detectingresistor and a differential circuit; wherein the controller generatesthe switching signal which disconnects the motor driving voltage fromthe motor when the motor drive current variation differs from the presetvalue by a predetermined amount; wherein a power terminal of thedifferential circuit is connected to the motor such that power issupplied to the motor drive current measuring means only when theswitching circuit connects the motor driving voltage to the motor. 2.The motor driving apparatus of claim 1, wherein the differential circuitincludes a first input connected to a first terminal of the detectingresistor, a second input connected to a second terminal of the detectingresistor, an output connected to the controller, and the power terminal.3. The motor driving apparatus of claim 2, wherein a first diode isconnected between a first terminal of the motor and the power terminalof the differential circuit, and a second diode is connected between asecond terminal of the motor and the power terminal of the differentialcircuit.